Switch debug_grpc_testlib to bind on localhost

Since there are no multi-machine tests, this is likely preferable from a
security standpoint to binding to all interfaces, and sidesteps the question of
cross-platform compatibility (some platforms may have IPV6_V6ONLY enabled by
default).
Change: 150358613

tensorflow/core/debug/debug_grpc_testlib.cc

@@ -68,7 +68,7 @@ GrpcTestServerClientPair::GrpcTestServerClientPair(const int server_port)
   }
 
   // Obtain server's gRPC url.
-  test_server_url = strings::StrCat("grpc://[::]:", server_port);
+  test_server_url = strings::StrCat("grpc://localhost:", server_port);
 
   // Obtain dump directory for the stream server.
   string tmp_dir = port::Tracing::LogDir();